This invention relates broadly to a composition and to a method for reducing the loss of water through permeable ground surfaces. Even more specifically, this invention relates to a composition having the properties of a binder such that when applied by the method of this invention to ground soils or sands, a strong, semi-permeable and flexible barrier is created below the surface. Even more specifically, this invention relates to a process for sealing the subsurface of porous agricultural lands so that they retain water and are more productive.
In many agricultural areas, water is a raw material of very considerable value. Particularly, in areas having little rainfall and no access to a ready supply of water, it is important that the water used for agricultural purposes not be immediately lost from the surface areas of the soil, through percolation to lower strata. In arid areas such as in the Western and Southwestern areas of the United States, where soils tend to be sandy and of a very porous and permeable nature, much of the available water supplies are lost due to seepage through the surface strata and accordingly the land cannot be used economically to grow crops.
While several methods have been developed in the art for impermeabilizing and consolidating ground soils as for example coating the ground surface with gunnite or waterproofing the ground surfaces with sheets of vinyl polymeric material or laying down other pavements of asphalt, these techniques are not suitable for impermeabilizing a lower strata of the soil, so as to retain the surface strata in a free, loose and agriculturally acceptable condition. The methods and compositions taught in grandparent application Ser. No. 457,969, now U.S. Pat. No. 3,891,586 and parent application Ser. No. 296,114, now U.S. Pat. No. 3,831,382 are eminently suitable for sealing and impermeabilizing surface strata and likewise the improved compositions and methods taught in copending application Ser. No. 566,283, filed April 9, 1975, now U.S. Pat. No. 3,979,916, are eminently suitable for sealing the surface strata.
The primary purpose of the instant invention is to provide a method and composition whereby agricultural soils can be treated so as to form a semi-pervious barrier at a selected depth below the surface, so that the surface soil remains loose and of the proper consistency for nurturing the roots of various plants. The sub-surface barrier must be semi-pervious because it is necessary that the surface soil drain, in order not to rot the roots of the growing plants. The sub-surface barrier created by the composition and methods of this invention permit either natural moisture or moisture from irrigation to be retained in the top strata of the soil for longer periods of time and thereby permit the plants to absorb water for biological processes. A further purpose of the instant invention is to reduce the waste of artificial nutrients and fertilizers which is inevitable where crops are grown in very porous soils and the nutrients drain with the irrigation or natural water past the roots and to lower levels where they are lost. A major problem in arid areas is not only the loss of the nutrient values by percolation through the soil, but also the runoff at lower strata of the fertilizer-bearing waters into estuaries and streams and the contamination of those streams with the phosphate, nitrate or other nutrient salts.
Other workers have attempted to create sub-surface, semi-pervious barriers, but these earlier methods have been largely inefficient, uneconomic or technically difficult to carry out. One method includes that of stripping the top soil from a given area and then constructing a water retaining barrier and thereafter recovering the stripped area with top soil. The large amount of work and expense inherent in this system is apparent.
Still another method has been developed wherein a specially designed auger is provided which creates an undercut slot below the surface, at a selected depth. Simultaneously while creating the slot, the auger sprays a liquid asphaltic media into the soil. The disadvantage of this technique is that special expensive equipment must be designed and the barrier which is produced is uneven and may therefore be more permeable than desired.
It is thus the primary object of this invention to provide a composition and method whereby a substratum, semipermeable barrier can be created at a selected depth beneath the surface of porous soils so as to make these soils useful for agricultural purposes.
It is a related object of this invention to provide a composition and method which is inexpensive and efficient to use and which will create a reliable barrier below the root levels of plants and will leave the surface soils in a loose condition so as not to interfere with the development of the growing plants.
It is a related object of this invention to decrease the loss of fertilizer and nutrients through percolation of same through ground soils and to decrease the pollution of streams and estuaries through sub-surface runoff of these nutrients and fertilizers.